1. Field of the Invention
This invention relates to air or gas sealing arrangements for rotating cylinders such as rotary kilns or the like, whereby the ingress and egress of diluent and contaminating gaseous fluids at the ends of the rotating cylinder are significantly reduced by the sealing arrangement.
The sealing arrangement of the present invention is an improvement over the sealing arrangement shown by U.S. Pat. No. 3,042,389 issued to David H. Gieskieng on July 3, 1962 and that shown by U.S. Pat. No. 4,209,175 to Robert M. Bliemeister dated June 24, 1980.
2. Description of the Prior Art
It is known in the prior art as taught by the aforementioned U.S. Pat. No. 3,042,389 of David H. Gieskieng to provide a self-counterweighted sealing ring for sealing the annular clearance space between a rotating cylinder such as a rotary kiln and a stationary structure such as a feed housing at one end of the rotating kiln or a firing hood at the opposite end of the rotating kiln, with respect to which the rotary cylinder rotates. The self-counterweighted annular seal of the aforementioned U.S. Pat. No. 3,042,389 has a self-counterweighted construction such that the center of gravity of the annular seal lies in a plane normal to the axis of rotation of the rotary cylinder which is axially displaced from the plane, also normal to the axis of rotation of the cylinder, in which the annular sealing ring contacts the outer surface of the kiln. This construction results in the creation of a force moment arm which causes the annular sealing ring to be continuously tilted into sealing engagement with the associated stationary structure, such as the stationary feed end housing at one end or the stationary firing hood at the opposite end of the rotating kiln. The seal construction just described substantially prevents leakage of gaseous fluid through the annular clearance space between the rotating cylinder and the stationary structures at the respective opposite ends of the rotating cylinder.
It is also known in the prior art as taught by the aforementioned U.S. Pat. No. 4,209,175 to Robert M. Bliemeister to provide an articulated seal for rotating cylinders of the type shown by the aforementioned U.S. Pat. No. 3,042,389 consisting of a plurality of circumferentially extending seal segments which are pivotally jointed to permit articulation of the joined segments in a plane perpendicular to the axis of the rotating cylinder to accommodate "out-of-round" portions of the circumference of the cylinder during relative rotary movement between the annular seal and the rotating cylinder.
As disclosed in the aforementioned U.S. Pat. No. 4,209,175, the seal hangs with loose contact on the upper surface of the rotating cylinder and hangs with a small clearance with respect to the lower surface of the rotating cylinder. This clearance is needed to permit the seal to walk along the shell of the rotating cylinder.
While a small clearance is needed to permit the seal to walk along the shell of the rotating cylinder, it is desirable not to allow the clearance to be any larger than necessary since a large clearance interfers with effective sealing.
In the past, the seal was fabricated and designed to allow for a small clearance. However, several problems have arisen. Since the cylinder normally operates at elevated temperatures, the kiln cylinder is prone to thermal expansion. Additionally, the seal, in contact with the cylinder surface, is also prone to thermal expansion. While the amount of thermal expansion of the seal and cylinder is taken into account in designing the seal dimensions to provide for an adequate clearance, the thermal expansion cannot always be predicted with adequate precision. Consequently, seals may be fabricated with too large a clearance, reducing seal efficiency, or with too small a clearance, inhibiting the ability of the seal to walk along the cylinder.